Overrunning brake for trailers

ABSTRACT

An overrunning brake is provided with a pull rod displaceably mounted in a pull tube, with a power transmission mechanically coupled to the pull rod for acting on the brake, and with a shock absorbing mechanism including a friction member positioned in the pull tube and prestressed for displacement between a pair of lugs. The friction member is operatively coupled to the pull rod with its friction face being forced against the pull rod.

United States Patent [191 Nicolay et a1.

[ 1 Mar. 11, 1975 OVERRUNNING BRAKE FOR TRAILERS [75] Inventors: Heinz Nicolay; Hans Griiner, both of Heidelberg, Germany [73] Assignee: Graubremse GmbH, Heidelberg,

Germany 22 Filed: Oct. 25, 1972 211 App]. No.: 300,747

[30] Foreign Application Priority Data Oct. 25, 1971 Germany 2152993 [52] US. Cl. 188/112 [51] Int. Cl ..B60t 7/20 [58] Field of Search 188/112, 129, 3 R

[56] References Cited UNITED STATES PATENTS 2,212,759 8/1940 Tea 188/129 2,235,340 3/1941 Stuart r 188/112 2,237,319 4/1941 Snyder 188/129 2,429,140 10/1947 Snyder 188/129 2,646,860 7/1953 Pirard 188/129 3,232,597 2/1966 Gaydecki 188/129 FOREIGN PATENTS OR APPLICATIONS 1,147,855 4/1963 Germany 188/112 814,246 7/1951 Germany 1,804,257 10/1968 Germany 188/112 914,216 3/1954 Germany 1,140,473 11/1962 Germany 1,228,154 11/1966 Germany 1,007,766 4/1902 France Primary ExaminerTrygve M. Blix Assistant Examiner-Galen L. Barefoot Attorney, Agent, or Firm-Roland I. Griffin [57] ABSTRACT An overrunning brake is provided with a pull rod displaceably mounted in a pull tube, with a power transmission mechanically coupled to the pull rod for acting on the brake, and with a shock absorbing mechanism including a friction member positioned in the pull tube and prestressed for displacement between a pair of lugs. The friction member is operatively coupled to the pull rod with its friction face being forced against the pull rod.

10 Claims, 10 Drawing Figures PATENTED 1 3.870, 128

sum 2 o g FIG. 3

PATENTED 3.870.128

fir-LU 3 UF 4 PATENTED H975- 3,870,128 sum If g OVERRUNNING BRAKE FOR TRAILERS BACKGROUND AND SUMMARY OF THE INVENTION This invention is related to overrunning brakes for trailers and, more particularly, to an overruning brake of the type including a pull rod displaceably mounted in a pull tube, a power transmission mechanism coupled to the pull rod and acting on the brake, and a shock absorbing mechanism positioned between the pull rod and the pull tube to absorb shocks and vibrations. Overrunning brakes of this type serve to connect a trailer with a pulling vehicle, to convert theoverrunning effect of the trailer into a load-controlled braking action, and to attenuate shocks and vibrations upon the starting and braking operations. It is necessary that such overrunning brakes include a braking threshold so that the braking effect is only caused when the braking threshold is reached. In addition, it is desirable to provide such overrunning brakes with some elasticity during the acceleration period.

Prior art overrunning brakes including hydraulic and mechanical mechanisms for attenuating shocks and vibrations are well known. In most cases hydraulic attenuators known as shock absorbers are used and'are operatively engaged between the pull rod and the pull tube. Shock absorbers of this type are complicated and difficult to manufacture. Moreover, in practical operation, they are subject to malfunction and have to be replaced because of wearing effects. The known mechan ical attenuators are also complicated, especially insofar as the construction of the pull rod and the pull tube is concerned. Furthermore, during thestar'ting movement an undesired continuous power increase is observed.

It is the object of this invention to provide a less complex overrunning brake that overcomes these deficiencies of the prior art and that provides an optimal braking action during the different operating conditions of the overrunning brake..It is especially desired to generate an essentially constant frictional force within the overrunning brake during the braking action as well as during the starting action.ln addition, it is desired to provide a braking threshold preventing-premature activation of the overrunning brake. It is further desired to provide a shock absorbing mechanism that serves as a pulling springduring acceleration.

These objectives are achieved according to the preferred embodiments of this invention by employing an overrunning brake in which the shock absorbing mechanism comprises a mechanically operating friction member positioned in the pull tube or a part thereof. This friction member is permanently prestressed and displaceably mounted between two lugs in the pull tube and is operatively coupled to-the pull rod with its friction face being forced against the pull rod. Equivalent construction can be provided where the friction member is supported by the pull rod or a part thereof forv stressing is increased. This prestressing should then be understood as an operating prestressing.

In order to establish a braking threshold for the overrunning brake,, the pull rod is provided with a further lug constructed and arranged with respect to the lugs in the pull tube so as to decrease the limited displacement of the friction member during the starting action of the trailer. Thus, it becomes possible to deflect the friction member further in the sense of increasing the friction force. Simultaneously, an elasticity effect is obtained during the starting motion.

According to one of the preferred embodiments, by which special advantages are obtained, the lug of the pull rod is only arranged and intended for the transmission of pulling force between the pulling vehicle and the trailer. Thus, an additional, presently-used mechanical lug between the pull rod and the pull tube for operatively branching the attenuating effect is no longer required.

The limited displacement of the friction member within the pull tube or a part thereof is adjustable. This adjustment, which, for example, can be obtained by screwing a locknut, simultaneously serves to adjust the basic prestressing. The lug supporting the friction member during the starting action of the trailer is wedge-shaped in order to increase the friction force on the friction member, which itself is provided with a corresponding wedge-shaped lug contact surface. The construction of the wedge-shaped lug and the corresponding wedge-shaped lug contact surface of the friction member is arbitrary so long as the friction force exerted on the pull rod at the frictionface of the friction member is increased by the wedge-shaped lug. On the other hand, the lug supporting the friction member during the braking action of the trailer is employed with a carrier disk that is either resiliently shaped or provided I with free spaces for housing a part of the mass of the friction member so as to decrease this friction force.

. For example, the essential part of this carrier disk can be made like a plate spring. The carrier disk is suitably made such that the friction between the friction member and the pull tube or a part thereof is kept rather small.

The friction member, especially in the area of the friction face, can be constructed differently depending on the, desired characteristic of the friction member. For example, the friction face may have an undulating or toothed surface. A toothed surface canted in one direction is advantageous for obtaining a directional friction force.

The subject matter of this invention allows different embodiments and equivalent constructions, the preferred ones of which are illustrated in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an overrunning brake according to one of the preferred embodiments of this invention.

FIG. 2 illustrates an overrunning brake according to another of the preferred embodiments of this invention.

FIG. 3 is a frictional force diagram illustrating the operation of the shock absorbing mechanism of FIGS. 1 and 2.

FIGS. 4-'-7 illustrate different positions of the shock absorbing mechanism of FIGS. 1 and 2 during different driving conditions.

FIGS. 8-10 illustrate different embodiments of the friction member of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, an overrunning brake according to the preferred embodiments of this invention includes a pull rod land a pull tube 2. Preferably, pull rod 1 and pull tube 2 are both tubular, and the pull rod is supported within the pull tube. A sideguard shaft 3 is fixedly connected topull tube 2, and a friction member 4 is supported around sideguard shaft 3 for limited displacement therealong as determined by a pair of lugs 5 and 6. Lug 5 has a wedge-shaped face 7 that matches an adjoining contact face 8 of friction member 4. A locknut 9 permits lug 5 to be displaced, adjusted, counter screwed, or otherwise fixed to sideguard shaft 3. Between friction member 4 and lug 6, which is preferably formed by a reduction in the diameter of sideguard shaft 3, there is provided a carrier disk 10. Carrier disk 10 can be a plate spring forming one or several free spaces as shown in FIG. 1 or may be flat as shown in FIG. 2,

Pull rod 1 includes a lug 12 at the end of the pull rod facing pull tube 2. Lug 12 may be constructed in the form of a perforated disk that surrounds sideguard shaft 3 with some clearance space and that is welded to pull rod 1. It is essential that lug 12 be positioned in the area of lug 6 in such a manner that lug 12 may abut upon carrier disk 10 to release the carrier disk from lug 6 and thereby further compress friction member 4. A transmission lever 13, which is located at a point spaced from the center of the longitudinal axis of pull tube 2 or beside sideguard shaft 3, abuts upon lug 12. Transmission lever 13 is pivotably mounted on a bracket 14. The braking linkage for the wheel brake operates on bore 15 of the transmission lever. A mounting plate 16, which is connected to bracket 14 or to pull tube 2, is in turn connected to the frame of the trailer.

The overrunning brakes illustrated in FIGS. 1 and 2 differ especially in the construction of the end of pull rod 1 facing pull tube 2. This end of pull rod 1 is outwardly bent and forms a shoulder 17 for abutting upon an attenuating ring 18 in the preferred embodiment of FIG. 1. The same end ofpull rod 1 is inwardly bent and provided with a fixed lug 12 in the preferred embodiment of FIG. 2 so that the only possible power transmission between pull rod 1 and pull tube 2 is that effected with friction member 4.

Although in the overrunning brakes illustrated in FIGS. 1 and 2 pull rod 1 is tubular andis guided in pull tube 2, other equivalent embodiments may be provided in which, for example, pull rod 1 has the greater diameter and houses pull tube 2. Friction member 4 may then be mounted on pull rod 1 or a part thereof. Other embodiments may also be provided that have no special sideguard shaft 3 and in which pull rod 1 or pull tube 2 directly form a support for friction member 4, this support being displaceable to a limited extent.

The operation of the overrunning brakes shown in FIGS. 1 and 2 will not be illustrated with the aid of FIGS. 3-7. In the diagram of FIG. 3 the ratio (in percent) of friction force (in kilograms) to trailer weight (in kilograms), hereinafter referred to as dimensionless friction force, is plotted along the ordinate as a function of overrunning path along the abscissa for three different operating conditions of the overrunning brake. The corresponding positions of the various parts of the overrunning brake of, for example, FIG. 2 are illustrated in FIGS. 4-7. In FIG. 3:

Point A corresponds to the driving position of the overrunning brake as shown in Flg. 4;

Point B corresponds to an intermediate position in the braking movement of the overrunning brake as shown in FIG. 5;

Point C corresponds to the turn over point between the braking movement and the starting movement of the overrunning brake as also shown in FIG. 5;

Point D corresponds to an intermediate position during the starting movement of the overrunning brake as shown in FIG. 6; and

Point E corresponds to the end phase of the starting movement of the overrunning brake as shown in FIG. 7.

As shown at point A in FIG. 3, the dimensionless frictional force between friction member 4 and pull rod 1 has a threshold value of 2-4 percent at the driving position of the overrunning brake shown in FIG. 4. This threshold value will be exceeded at the beginning of the braking action. The threshold value is determined by the basic prestressing of friction member 4 between lugs 5 and 6 as well as by the prestressing due to the pulling force. The prestressing due to the pulling force is caused because, as shown in FIG. 4, carrier disk 10 is positioned in abutment upon lug 12 (or the corresponding inwardly bent end of pull rod 1 that may also be considered as a part of lug 12) rather than lug 6.

During the braking action, the dimensionless frictional force between friction member 4 and pull rod 1 is constant over the overrunning path and amounts to about 1 percent as shown in FIG. 3. At an intermediate position during the braking action, as shown at point B in FIG. 3, pull rod 1 has moved relative to pull tube 2, which is kept stationary in FIGS. 4-7. Thus, as shown in Flg. 5, carrier disk 10 is released from lug l2 and positioned in abutment upon lug 6, and the friction force I is transmitted from-pull rod 1 onto friction member 4 and therefrom to sideguard shaft 3. The resultant deflection of friction member 4 simultaneously retracts it to, a certain extent from lug 5.

At the turnover point between the braking action and the-starting action of the overrunning brake, as shown at point C in FIG. 3, substantially the same conditions exist as already discussed above in connection with FIG. 5. The slight decrease of the friction force does not lead to a significant change in the relative positions of'the various parts of the overrunning brake.

At an intermediate position in the starting action of the overrunning brake, as shown at point D in FIG. 3, pull rod 1 again transmits friction force to friction member 4, but this time in a reverse direction, as shown in FIG. 6. This pulls friction member 4 onto the wedgeshaped face 7 of lug 5 where a corresponding deflection of the friction member takes place. This deflection becomes sufficiently great to release friction member 4 from lug 6. In order to increase the friction force transmitted to friction member 4 as a function of the velocity, lug 5 has a wedge-shaped face 7 (in contrast to lug 6). The inclination of the wedge angle can be determined by experiments according to the desired increase in the friction force. As shown at point D in FIG. 3 the increased dimensionless friction force at this position is about 50-60 percent.

As the starting movement of the overrunning brake progresses, pull rod 1 moves further and further out of pull tube 2 until lug 12 engages carrier disk and thereby additionally prestresses friction member 4 as shown in FIG. 7. At the end of the starting movement, as shown at point E in FIG. 3, the compression of friction member 4 causes a stepwise increase in the dimensionless friction force, when then amounts to about 100 percent.

The peak dimensionless friction force, shown at point E in FIG. 3, represents a starting spring effect of the starting action. Thus, friction member 4 simultaneously serves the function of what is otherwise known as the starting spring. As soon as the pulling vehicle operates with its desired movement, the effect of the starting spring ends and the dimensionless force adjusts to the threshold value.

For attenuating shocks and vibrations it is important that lugs 5 and 6 be made differently. Lug 5 on which friction member 4 is supported during the starting action of the trailer (see FIGS. 6 and 7), is wedge-shaped in order to increase the friction force applied to the friction member. The contact face 8 of friction member 4 corresponds to the wedge-shaped face 7 of lug 5 and, depending on the desired effect, may either make surface contact or point contact therewith. A lug 5 having combined wedge angles could also be used so that friction member 4 could be supported at two different positions thereon. Lug 6 and carrier disk 10 are constructed so that a decrease in the dimensionless friction force is obtained when friction member 4 and carrier disk 10 are supported in abutment uponlug 6 during the braking action (see FIG. 5). For example, carrier disk 10 may be formed like a plate spring so that the carrier disk becomes resilient. As shown in FIG. 1, carrier plate disk 10 may also be rigidly formed and provided with free spaces 1 1 into which a part of the mass of friction member 4 can yield during the braking action (shown in FIG. 5) to decrease the friction applied to the friction member.

In FIGS. 8-10 several'different embodiments of friction member 4 are illustrated in which the contact surface 8 has different slopes and in which the friction face is flat (FIG. 8), undulated (FIG. 9), or toothed (FIG. 10). The embodiments of FIGS. 8 and 9 illustrate friction faces for which the transmitted friction force is independent of the axial direction of movement of friction member 4, while the embodiment of FIG. 10 illustrates a friction face for which the transmitted friction 1. An overrunning brake for a trailer, said brake '7 comprising a first pull member displaceably mounted in a second pull member, power transmission means coupled to the first pull member for acting on the brake, and shock absorbing means positioned between the first and second pull members for absorbing shocks and vibrations, said shock absorbing means including a mechanically operating friction member positioned in the second pull member and prestressed for displacement between first and second lugs fixedly positioned in and attached to the second pull member, said friction member being operatively coupled to the second pull member and having a friction face forced against the first pull member, and said first pull member being provided with a third lug adapted for movement to a position between the first and second lugs so as to shorten the displacement of the friction member between the first and second lugs during starting action of the trailer and for movement to another position so as not to shorten the displacement of the friction member between the first and second lugs during braking action of the trailer.

2. An overrunning brakeas in claim 1 wherein said first, second and third lugs are axially aligned within the second pull member, said positions are disposed on opposite sides of the second lug, and said third lug is provided with a clearance opening permitting it to move relative to the second lug between said positions.

3. An overrunning brake as in claim 2 wherein said third lug is only constructed for transmitting pulling force between the trailer and a pulling vehicle therefor.

4. An overrunning brake as in claim 2 including means for adjusting the displacement and, hence, the prestressing of the friction member between the first and second lugs.

5. An overrunning brake as in claim 2 wherein the one of said first and second lugs upon which the friction member abuts during the starting action of the trailer is wedge-shaped to increase the friction force acting against the first pull member, and said friction member includes a correspondingly shaped contact surface.

6. An overrunning brake as in claim 2 including a resilient carrier member upon which the friction member abuts during the braking action of the trailer to decrease the friction force. 1

7.An overrunning brake as in claim 2 including a carrier member upon which the friction member abuts during the braking action-of the trailer, said carrier member being provided with free spaces for receiving a part of the mass of the friction member.

8. An overrunning brake as in claim 2 wherein said friction member includes an undulated friction face.

9. An overrunning brake as in claim 2 wherein said friction member includes a toothed friction face.

10. An overrunning brake as in claim 2 wherein said friction face is adapted to provide a directional friction force. 

1. An overrunning brake for a trailer, said brake comprising a first pull member displaceably mounted in a second pull member, power transmission means coupled to the first pull member for acting on the brake, and shock absorbing means positioned between the first and second pull members for absorbing shocks and vibrations, said shock absorbing means including a mechanically operating friction member positioned in the second pull member and prestressed for displacement between first and second lugs fixedly positioned in and attached to the second pull member, said friction member being operatively coupled to the second pull member and having a friction face forced against the first pull member, and said first pull member being provided with a third lug adapted for movement to a position between the first and second lugs so as to shorten the displacement of the friction member between the first and second lugs during starting action of the trailer and for movement to another position so as not to shorten the displacement of the friction member between the first and second lugs during braking action of the trailer.
 1. An overrunning brake for a trailer, said brake comprising a first pull member displaceably mounted in a second pull member, power transmission means coupled to the first pull member for acting on the brake, and shock absorbing means positioned between the first and second pull members for absorbing shocks and vibrations, said shock absorbing means including a mechanically operating friction member positioned in the second pull member and prestressed for displacement between first and second lugs fixedly positioned in and attached to the second pull member, said friction member being operatively coupled to the second pull member and having a friction face forced against the first pull member, and said first pull member being provided with a third lug adapted for movement to a position between the first and second lugs so as to shorten the displacement of the friction member between the first and second lugs during starting action of the trailer and for movement to another position so as not to shorten the displacement of the friction member between the first and second lugs during braking action of the trailer.
 2. An overrunning brake as in claim 1 wherein said first, second, and third lugs are axially aligned within the second pull member, said positions are disposed on opposite sides of the second lug, and said third lug is provided with a clearance opening permitting it to move relative to the second lug between said positions.
 3. An overrunning brake as in claim 2 wherein said third lug is only constructed for transmitting pulling force between the trailer and a pulling vehicle therefor.
 4. An overrunning brake as in claim 2 including means for adjusting the displacement and, hence, the prestressing of the friction member between the first and second lugs.
 5. An overrunning brake as in claim 2 wherein the one of said first and second lugs upon which the friction member abuts during the starting action of the trailer is wedge-shaped to increase the friction force acting against the first pull member, and said friction member includes a correspondingly shaped contact surface.
 6. An overrunning brake as in claim 2 including a resilient carrier member upon which the friction member abuts during the braking action of the trailer to decrease the friction force.
 7. An overrunning brake as in claim 2 including a carrier member upon which the friction member abuts during the braking action of the trailer, said carrier member being provided with free spaces for receiving a part of the mass of the friction member.
 8. An overruNning brake as in claim 2 wherein said friction member includes an undulated friction face.
 9. An overrunning brake as in claim 2 wherein said friction member includes a toothed friction face. 